Apparatus for drying and treating wet granular materials



G. A. VISSAC 2,083,756

APPARATUS FOR DRYING AND TREATING WET GRANULAR MATERIALS- June 15, 1937.

Original Filed Aug. 11, 1936 2 Shegts-Sheet l .rmvg AvbRE VISMC W 6 W G. A. VISSAC June 15, 1937.

APPARATUS FOR DRYING AND TREATING WET GRANULAR MATERIALS Original Filed Aug. 11, 1936 2 Sheets-Sheet 2 Patented June 15, 1937 UNITED. STATES PATENT OFFICE MATERIALS Gustave Andre Vissac, Calgary, Alberta, Canada Original application August 1 1, 1936, Serial No.

95,419. Divided and this application January 21, 1937, Serial No. 121,698

"lClaims.

This invention relates to an apparatus for drying and treating wet granular materials, and is a division of original application, Serial No. 95,419, filed August 11, 1986.

" Difierent methods and apparatus for effecting the drying and preparation of wet granular ma-' terials have been suggested and used heretofore. However, the methods and apparatus previously employed have had serious disadvantages. Wet granular materials have been dried in vertical or rotary driers and on screens but degradation of coal, among other things, is apparent in the use of rotary driers and, in other types of apparatus, there has been the difiiculty of penetrating a bed of coal lying on top of a screen or conveyor with currents of air which generally tend to pack the bed and retard or prevent movement of the material. Furthermore, difilculty has been encountered in controlling the gas temperature while using ordinary types of furnaces. Lack of efliciency has, therefore resulted.

For many years it has been the practice to treat materials to prevent deterioration and, in the case of coal, it has been well known to subject the product to an oil treatment in order to prevent deterioration and to control the dust. There has been experienced, however, difiiculty in distributing the oil over the particles to render the coal dustless when properly dried.

It is an object of the present invention to provide a novel apparatus for drying and treating wet granular materials including coal so as to avoid apparent disadvantages in previously used apparatus and to provide in a simple manner 35 means for the drying and treating of material quickly and efliciently.

A further object of the invention is to provide an apparatus which may be operated with the use of a minimum volume of air, wherein the air is 40 caused readily to penetrate the bed of material being dried without aflecting the movement of the material to any extent.

A further object of the invention is to provide an apparatus wherein heated gases may be employed for penetrating the bed of material to eliminate the moisture.

A still further object of the invention is to provide an apparatus wherein the material may be coated in a practical way with an agent such as oil, in the case of treatment of coal, the agent being incorporated with the heating gases to spray and contact all particles of the material in the bed undergoing drying.

A still further object of the invention is to 55 provide an apparatus constructed and arranged so that the various elements co-operating to eflect drying and, treatment are minutely controlled to such a degree as to provide for a final efficiently dried product and in a large volume comparative to the time of operation.

With these and other objects in view, the invention will be apparent upon a consideration of the following specification in conjunction with the accompanying drawings which form part of the application.

In the drawings: v

Figure 1 is a schematic side view of apparatus for drying and treating the material.

Figure 2 is a schematic view of one of the screens employed, to show the course taken by the material under normal conditions during the oscillation of the screen.

Figure 3 is a sectional view of a nozzle construction for mixing and ejecting thetreating gases.

Figures 4 and 5 are schematic views to illustrate the course taken by the material as it passes through the apparatus.

Figure 6 is an enlarged sectional detail taken on the line 5-6 of Figure 1 to illustrate the drive for the pulsators.

Referring more particularly to the drawings, A and B indicate two compensating shaker screens supported by suitable oscillatable hangers HI and H. The screens are preferably covered with a wire mesh, perforated plates or wedge wire screen surfaces of proper mesh and are connected to eccentrics l2 through connecting rods l3 disposed preferably at an 180 angle, so that when the eccentric I2 is operated through any suitable source, such as the motor H, the screens are subjected to opposed and continuous oscillation.

The wet granular material is delivered from the chute I5 on to screen A, which is divided into two sections CD and DE. The material, after passing over screen A, is transferred to screen B and this latter screen is likewise divided into two sections FG and GH, these sections being defined by the area between the transverse lines indicated by these various letters. On screen A the material is delivered first of all to section CD, below which is positioned a suitable hood l6 connected by a pipe I! to a water sump i8. As the material passes over section CD, the excess moisture carried thereby is caused to pass through the screen by gravity and the momentum of the material owing to the shaking motion of the screen.

After passing over the area CD of the first screen, the partially dewatered material is moved over section DE above which is positioned a hood l8 which is connected by a pipe line l9 and 20 with the boiler 2i of a furnace C and is also connected in a suitable manner by pipe lines 22 and 24 with the flue 24 of the furnace C so that steam and hot flue gases are discharged into the hood and pass through the bed of coal on the screen. The pipe lines connected with the hood may be arranged in any suitable manner and may take the form of pipe lines which commonly communicate with the hood as shown. Furthermore, in the case where the coal or other material being dried is also to be treated, other apparatus for treatment may be incorporated at this point. For instance, in the case of coal, if it is desired to treat it with 011, an oil line 35 may be incorporated with the pipes l9 and 22 and discharged with the gases through a suitable nozzle, as will hereinafter be described.

The steam and flue gases projected into the hood l8'serve to warm the coal and the condensed steam is shaken oil and eliminated with the excess of condensed moisture of the coal, Below section DE are positioned hoods 26 and 21 communicating through pipes 28 and 29 with the conduits 30 and 3| respectively. These conduits preferably commonly communicate as at 32 with a suction fan 33 in turn communicating with an evas 34 which, through the drainage pipe 35, delivers the moisture to the water sump l8. In the conduits 30 and 3|, in advance of the fan 33, are positioned pulsators 36 and 31 respectively which are disposed oppositely to one another alternately to establish connection between the fan and conduits 30 and 3|. The pulsators are held in relative opposed position and are driven by a suitable drive such as the driving gear 36 and sprocket-31" preferably connected by a chain to the shaft carrying eccentrics I2. Thus so that in a particular manner, by means of air currents, the coal is heated and the moisture is withdrawn when the coal is positioned in section DE of the screen A, as will be described more particularly hereafter.

The coal is then passed from screen A to screen B and is delivered to section FG over which is positioned a hood 38 connected by the pipe 39 with the pipe line 23 so that hot flue gases are passed to hood 38 and passed through the bed of coal lying on the section FG which was already heated in the previous section. The hot gases pass through the bed of coal and are discharged into hoods 40 and 4| which communicate by means of pipes 42 and 43 with conduits 30 and 3| respectively and are brought into communication with the fan as in the case of the prior two hoods. The hot gases pass through the bed of coal, subjecting the coal to an intense drying action, so that the moisture is largely eliminated when the coal passes from this section. As the coal moves on to section GH it is subjected to a final drying and cooling operation. In this instance it will be noted that the pair of hoods 44 and 45 are positioned beneath section GH and communicate respectively with the conduits 30 and 3|. The upper side of the screen in section GE is completely open to the atmosphere so that through the action of the fan 33 cool air is drawn through the bed of coal so that a final effective drying operation takes place at this point in addition to the cooling of the coal before it is loaded into barges, etc., thus avoiding possible oxidization during transit due to a heated condition.

When coal is discharged Onto a shaker screen and subjected to continuous downward current of air, it packs and becomes difllcult to move and the air currents cannot penetrate the bed eiiiclently in intimate contact with all particles of the coal. However, under the present development by the use of proper pulsations of air properly combined with the shaking motion of the screen, having regard to periods of compression and depression of the mass of coal on the screen, a free motion of the coal on the screen is obtained and the air thoroughly penetrates and intimately contacts with the coal particles throughout the bed. The same is true of the gases and steam and a treating agent such as oil, in the case of coal, if used.

On referring particularly to Figure 2, wherein the motion of the coal on the screen is illustrated, CA represents a coal particle on the surface SA. The particle CA being inert, follows the motion of the screen and reaches the position CB. After the screen has reached the position SB, it stops and then returns to SA but the coal from its momentum continues to position CC and then under the action of gravity falls to the position CD on the screen SA. Consequently for each complete oscillation of the screen the coal advances a distance equal to CA-CD. However, if during this complete oscillation of the screen, a downward current of air or gases is continuously maintained over the surface of the screen, the coal instead of leaving the screen at CB will be continuously pressed on the screen and return with it to CA. To avoid this I employpulsating currents, which, on the contrary, are established and disestablished in such a way as not to blow down in at least part of the forward and return motion of the screen. Thus the coal will not be held on the screen but will be permitted to move to an extent such as referred to above, although the relative displacement of the coal will be slightly decreased. Therefore, according to the present development, the air and gases are intimately contacted with the particles of coal making up the bed since the air and gas can readily penetrate the bed as it is agitated and the coal continuously passes along in an eflicient manner through the various stages of treatment on the screen.

As an illustration, assume the screen to be oscillating at 240 periods per minute and air pulsating at the rate of 480 pulsations per minute, this results in one quarter of a second for complete oscillation of the screen whose displacements are positive for the upstroke of the screen (compression of the coal) and negative for the downstroke (compression of the coal). gas pulsations are positive when a connection is established with the fan 33 through the pulsators 36 and 31, causing a strong current of air to be established downwards over a portion of the screen. Pulsations are negative when the pulsator is closed on the pipe line to which the particular hood considered is connected. During the closure of the pulsator there is no downward current of air on the coal in the area overlying the hood whose pipe line is closed. 0n the contrary, with the closure of a pulsator, a slight upward current of air is produced due to a returning wave of the air pulsation.

To illustrate the action, reference is made to Figure 1 and Figures 4 and 5, which illustrate the action of a piece of coal lying upon the screen above the hood 26, a similar action occurring above the hoods 21, 40 and 4|. Upon referring to Figure 1, it will be seen that hood 26 is illustrated Air and as connected to pipe line 3| which is closed of! from the fan by the pulsator 31. Consequently, assuming that the screen is moving forwardly at this point, it will be realized that there is a nega- 5 tive pressure on the coal. Thus when the screen moves one-half the distance of its forwardmovement, the piece of coal CO will reach the position CP (see Figure 5). At this point the pulsator 31 is reversed to establish a positive downward pressure of air, whereupon the piece of coal will be moved back towards the screen, reaching substantially the position CQ and, moving upward with the screen, will reach the position CR. At this point the pulsator again changes, establishing a negative or slightly upwardly directed current of air, and as the screen moves back in downstroke through one-half its movement in .this direction, the piece of coal will be free and reach substantially the position CS. At this point 0 the pulsator again changes, establishing a downward pressure of air which will cause the coal to move downwardly to reach substantially the position CT, so that during one complete oscillation of the screen under the conditions referred to the coal will move along the screen a distance substantially equal to CO-CT. The coal moves this distance in one-quarter of a second, having regard to the ratio as between the air'pulsations and screen oscillations, so that during the period of one second the coal will be caused to move substantially four times this distance during which time it will be subjected to Four periods of active forward motion, Four periods of aeration,

Four periods of slightly assisting motion, Four periods of slightly assisting aeration.

A similar action takes place on the other half of the screen section underlying the hood I8 and i overlying the hood 21, although the action of the air current is substantially reversed for the reason that the hood 2? is, as illustrated in Figure 1, in direct connection with the fan due to the fact that the pulsator 36 is in the open position. Therefore, assuming that the screen is moving forwardly at this point, the coal will be subjected to a downwardly directed current during the first part of this movement.

On referring to Figure 4, it will be seen that as the screen moves forwardly a distance equal to one-half its travel the coal CL is subjected to a positive downward pressure so that it will be held on the screen and reach the position CK at the halfway mark. At this point the pulsator 36 reverses and a negative pressure is established so that, as the screen travels forwardly the last half of the distance, the coal will reach substantialiy the position CM. At this point downward pressure is again established so that the coal is impelled downwardly and slightly forwardly till it reaches the position CN, at the half-way mark in the downward movement of the screen, whereupon a negative pressure is again established so that it is loose on the screen and when the screen reaches the extreme lower position in its downward movement the coal will reach substantially the position CX. Consequently the coal moves a distance equal to CL-CX in a similar manner to the operation above referred to. It is apparent, therefore, that there is a constant forward movement of the coal while subjected to varying air currents and thus, in addition to securing proper motion of the coal, there is provided the most eflicient conditions for heating and drying the coal as well as oiling when it is proposed to give the coal an oil treatment.

The eccentrics I! have an adjustable stroke which provides for regulation of the total displacement of the coal, due consideration being given to losses due to compression periods to obtain the desired output compatible with the total duration of the treatment periods necessary to obtain the desired results.

An important feature of the invention resides in the fact all the hoods under the screen are of exactly the same shape and size, so that they all can be resonators to the same notes of music or to the same air pulsations Qfcertain periods; in other words, all harmonics.

The driving motor I4 is designed to provide a very sensitive variable speed drive and, when the system is put into operation, resonance is obtained by tuning to the ear. The adjustment of the speed of the motor permits one to catch the desired period of air pulsation for which all the air boxes or hoods are resonators. This results, therefore, in a considerable increase in efllciency; instead of air currents counteracting against each other and waste of energy, there is a considerable amplification of these air currents. Consequently maximum volumes of air are circulated for minimum of energy supplied which results in maximum efficiency in heating, drying and oil spraying when this is carried out.

The efliciency of the apparatus is readily illustrated by referring to operation with screens of a size to provide a width of 4 feet and lengths of 6 to 7 feet for sections CD, DE, FG and GH, which provide for a tonnage of 50 tons per hour of coals over one-eighth of an inch in size. During passage of this volume of material over the screens the moisture content was reduced on section CD down to 12 to 14% and at the end of section GH down to a moisture content of 2 or 3%.

As a result of the processing in the apparatus described the coal as it is discharged is just suitable for shipment. It will not freeze in the winter time and not oxidize to any extent. However, during its transportation in barges or railway cars it is liable to deteriorate. Fines will therefore be made, thus producing an objectionable dust when the coal is delivered to the consumer. for many years and may be particularly and suitably applied in this apparatus. Through its addition'with the hot gases in the drying operation the oil, as previously referred to, is introduced through the pipe line 25 to the hood 68. To be efficient the oiling must disseminate the oil and. throw it in contact with the whole mass of the coal equally and regularly. This is readily brought about with the introduction of the oil along with the gas during the agitation of the coal as previously described. In other words, the gases through the pulsating arrangement project through the loose mass of coal so that a large volume travels through the coal and comes into intimate, contact with the whole mass. 4 The oil is heated to a fluid and thrown under pressure by a pump as usual, but when ejected it is carried by a strong and large volume of hot gases and by steam through the coal as the latter, when loose, is aerated and dried. In this way all particles of coal have a chance to receive a thin film of oil, and as the oiling is regular it is accompanied with a minimum. consumption of oil. A relatively cheap oil can be used when it is applied to the coal as described in view of To control the dust, oil has been used 1 the efiicient heating and spraying action which takes place.

To spray the oil a special construction may be employed, for instance, in the gas conduit 22 there will be arranged an oil ejecting construction composed of the pipe line 46, corresponding to pipe l9 illustrated in Fig. 1, into which the oil jet 4?, controlled by needle valve 48, is projected. Also communicating with this pipe is the steam conduit 20. Within the pipe 46, below the oil ejector, are positioned the mixing cones 50 and 5| through which the oil is directly ejected, the wide ends of the cones permitting the steam to intermingle with the oil. At the lower end of the pipe 36 is provided further mixing cones 53 and 54 which permit the hot gases in the conduit 22 to pass into intimate contact with the intermixed steam and oil, so that, as the mixture is projected into the hood l8, there is a very fine composite mixture of hot gas, steam and oil which readily penetrates the loose bed as de scribed and contacts with the whole mass of coal equally and regularly.

Moreover, due to the fact that the oil is piped to the hood within the pipe 46, which acts to carry the steam, the oil is readily heated to a proper degree and the construction, in addition to ensuring a good mixing, acts as a blower injector. There is no danger of the oil evaporating as an oil of high boiling point may be selected.

As an example of the air and oil consumption for conditions, sizes and tonnages as above referred to, a volume of around 25,000 cubic feet of air and gases passes constantly through the apparatus and the amount of oil used is two to three pounds per ton.

The heating system provides a marked advance and contributes to the success and efilciency of the apparatus disclosed. Most driers use hot gases from a furnace in coal drying as accomplished at the coal mine and plenty of low grade and cheap coals are available and used. However, in such furnaces as the gases produced by such coal can run as high as several thousand degrees, their use introduces many problems. For instance, most coals begin to oxidize at 200 C. and this oxidization is likely to alter their coking and burning qualities and if carried further will cause ignitions or explosions. ing to the present invention, however, by employing steam, the heat of the combustion gases is first used to produce the steam and when the gases leave the boiler they are always at a temperature under the danger point so that they can be passed through the coal mixed with air, if necessary to obtain the desired volume, without any possibility of disadvantageous results. In view of this, quick and efiicient drying is accomplished in a relatively simple type of apparatus.

As a further illustration of this in an apparatus of the dimensions above referred to, the coal advances one inch for a screen oscillation of two inches, and therefore when operating at 240 oscillations of the screen per minute, this results in the coal advancing four inches per second. Thus for a bed of a thickness packed to four inches, an output of 50 tons per hour is achieved. It is apparent upon consideration of the foregoing that the apparatus provides for eflicient drying, wherein a percentage of moisture is removed by gravity and the remainder successively eliminated by heating and preheating with steam and gases, drying with gas and drying with air. In addition the apparatus is particularly efilcient through the employment of Accordcontrolled air pulsations which when combined with the heating provides for quick drying, as well as a steady movement of the material. The apparatus therefore by a combination of mechanical drying through agitation, heat exchange by steam and hot gas, and evaporation by intense gas circulation in a loose mass, provides for the efllcient treatment of large volumes of material with a relatively small consumption of air, heat and power. In addition it provides the most eflicient conditions for treatment of the material, such as by oil in the case of coal, inasmuch as the oil may be readily dispersed and brought into intimate contact with the coal particles.

However, it will be realized that while coal has been used as a general illustration of the material treated, the apparatus is generally applicable to the drying of wet granular materials and that where materials are subjected to treatment by special agents, such agents might be brought into contact with the material in a similar manner to the dispersion of the oil as above referred to.

Various modifications may be made in this invention without departing from the spirit thereof or the scope of the claims, and therefore theexact forms shown are to be taken as illustrative only and not in a limiting sense, and it is desired that only such limitations shall be placed thereon as are disclosed in the prior art or are set forth in the accompanying claims.

What I claim as my invention is: I

1. Apparatus for drying wet granular material, comprising a shaking screen for receiving and agitating the material, a hood disposed below said screen, a hood disposed above the screen in an area overlying the lower hood, air inducing means, a conduit connected between the lower hood and said air inducing means, pulsating means for establishing and disestablishing direct connection between the air inducing means and lower hood, and means for introducing steam to the upper hood whereby said steam is drawn through the material on the screen into intimate contact with it while said material advances therealong, to preheat said material.

2. Apparatus for drying wet granular material, comprising a shaking screen for receiving and agitating the material, a hood disposed below said screen, a hood disposed above the screen in an area overlying the lower hood, air inducing means, a conduit connected between the lower hood and said air inducing means, pulsating means for establishing and disestablishing direct connection between the air inducing means and lower hood, and means for introducing steam and hot gases to the upper hood whereby said steam and hot gases are drawn through the mate rial on the screen into intimate contact with it while said material advances therealong, to preheat and dry said material.

3. Apparatus for drying wet granular material comprising a shaking screen for receiving and agitating the material, a plurality of hoods disposed below the screen, a hood disposed above the screen in an area overlying the lower hoods, air inducing means. conduits connected between the lower hoods and said air inducing means, pulsating means for alternately establishing and disestablishing direct connection between the air inducing means and each of said lower hoods, and means for introducing steam to the upper hood whereby said steam is drawn through the material on the screen into intimate contact with air inducing means, pulsating means for establishing and disestablishing direct connection between the air inducing means and the lower hoods, means for introducing steam to at least one of said upper hoods as a preheating medium, and means for introducing hot gases to at least one of the upper hoods as a drying medium whereby said steam and hot gases are drawn by the pulsating means through the material on I the screens, to preheat and dry said material while it advances along the screens.

5. Apparatus for drying wet granular material comprising a plurality of shaking screens for receiving and agitating the material, a plurality of hoods disposed below said screens, a plurality of hoods disposed above the screens in areas that overlie the lower hoods, air inducing means, conduits connected between the lower hoods and the air inducing means, means associated with the air inducing means for causing pulsating air'currents to pass through the bed of material through said lower hoods, said upper hoods and said lowerhoods respectively being of corresponding size and shape whereby all the induced air currents are caused to resonate with one another, and

means for introducing preheating and drying mediums to the upper hoods whereby said preheating and drying mediums are drawn by the pulsating air currents through the material on the screens while it advances along the screens, to preheat and dry said material.

6. Apparatus for drying wet granular material comprising a shaking screen for receiving and agitating the material, a plurality of hoods disposed below the screen, a hood disposed above the screen in an area overlying the lower hoods, air inducing means, conduits connected between the lower hoods and said air inducing means, pulsating means for alternately establishing and disestablishing direct connection between the air inducing means and each of said lower hoods, a furnace including a boiler heated by combustion gases tolproduce steam, and a flue for discharging the combustion gases, means for introducing the steam to the upper hood, means for connecting the flue with the upper hood to discharge the combustiongases thereinto and onto the bed of material, said steam and gases being drawn by the pulsating means through and into intimate contact with the material on the screen, to preheat said material while it advances along the screen.

7. Apparatus for drying wet granular material comprising a plurality of shaking screens for receiving and agitating the material, a plurality ofhoods disposed above said screens for receiving and projecting a heating and drying medium onto the material, a plurality of hoods disposed below the screens underlying the upper hoods, and means connected with said lower hoods for inducing pulsating air currents to draw the heating and drying medium through the agitated bed of material as it moves along the screens.

aus'ravn ANDRE VISSAC. 

